Bar code scanners are used in a wide variety of applications that rely on information stored in bar codes. Industries such as retail, airline, self-service, automotive, parcel delivery, pharmaceutical, healthcare and others use bar codes to provide inventory control, customer identification, item tracking, security and many other functions. A typical bar code is comprised of a number of bars separated by spaces. Information is encoded on a bar code by varying the width of the bars and spaces. When a bar code is placed within the field of view of a bar code scanner, the scanner will detect, analyze and decode the bars and spaces comprising the bar code to retrieve the information encoded wherein. This operation is also called scanning or reading a bar code. The information encoded on a bar code is usually a sequence of numeric or alphanumeric symbols (e.g., a Universal Product Code (UPC) or European Article Number (EAN)).
An imaging bar code scanner (also referred to as an image scanner) reads a bar code by capturing a digital image of the bar code and then processing the image to detect and decode the bar code. It is advantageous for the bar code scanner to successfully read all bar codes presented to the scanner on the first pass of each bar code by the scanner. This is known as a successful first pass read. Successful first pass reads of bar codes helps to maintain a good workflow at the checkout station and speeds up the overall checkout process. A high success rate for first pass reads has also been found to reduce stress on the person operating the scanner. This is particularly true if the operator is a customer operating a self-checkout terminal.
High performance passby barcode scanners based upon image capture and image processing technology have been slow to be adopted in passby scanning environments. In a retail environment, an image scanner must achieve an object passby speed of 30 to 50 inches per second. The image scanners on the market today have not proved capable of such speeds, which is one reason why laser based barcode scanners dominate the passby scanning environments.
One important barrier that has prevented image scanners from reaching high passby speeds is the amount of time required to extract sufficient pixel data from an image capture device to identify and decode an optical code contained in a captured image. Usually only a small portion of a captured image contains an optical code so only the pixel data for that portion is required to be extracted from the image capture device for decoding. Unfortunately, the optical code can appear anywhere within the captured image so more than just the pixel data representing the optical code has to be extracted from the image capture device and analyzed. Extracting all pixel data from an image capture device is very time consuming and extracting blocks of pixel data requires issuing commands to the image capture device for each block extracted which is also time consuming.
Therefore, it would be desirable to provide an image capture device that does not suffer from this problem.